Structures capable of realizing a small-sized pressure sensor by simplifying the internal structure of the pressure sensor have been proposed (for example, International Patent Application Publication No. JP 2003-529070 which corresponds to U.S. Pat. No. 6,810,746) FIG. 8 is a schematic sectional view showing a pressure sensor in a related art. As shown in FIG. 8, the pressure sensor is so constructed as to include a housing J1, a hexagonal casing J2, and a device connector J3.
The housing J1 is fixed to the hexagonal casing J2 in such a way as to pass through it. A pressure introducing port J4 is provided in one end of this housing J1 and a pressure measuring cell J5 provided with a diaphragm is arranged at the terminal portion of this pressure introducing port J4. This pressure measuring cell J5 is electrically connected, via the contact surface J7 of a substrate J6 having an integrated circuit, to the integrated circuit in the substrate J6. Further, the integrated circuit in the substrate J6 is electrically connected via a compression spring (plate spring formed in the shape of a letter S) J8 to a connector contact J9 placed in the device connector J3. Still further, the connector contact J9 is electrically connected to a terminal J10.
The device connector J3 is fixed to the hexagonal casing J2 in such a way as to cover the pressure measuring cell J5, the substrate J6, and the compression spring J8 to construct a package. Here, the device connector J3 has an external connector (not shown), thereby being electrically connected to an external device.
In the construction described above, the integrated circuit in the substrate J6 is electrically connected to the connector contact J9 by the compression spring J8 formed in the shape of a letter S. Specifically, one end of the compression spring J8 is directly connected to the substrate J6 by a conductive adhesive. On the other hand, the other end of the compression spring J8 is adapted to be put into contact with the connector contact J9 placed in the device connector J3 when the device connector J3 is fitted into the hexagonal casing J2. In this manner, the state of electrical conduction between the integrated circuit in the substrate J6 and the connector contact J9 is set.
However, in the above-described conventional structure having the state of electrical conduction by the compression spring J8, there is presented a problem that when the pressure sensor suffers external vibrations, the compression spring J8 resonates with the external vibrations. Here, one end of the compression spring J8 is directly connected to the substrate 6 but the other end of the compression spring J8 is only pressed onto and fixed to the connector contact J9. Hence, there is a possibility that when the compression spring J8 suffers and resonates with the external vibrations, the other end of the compression spring J8 might be brought to a state in which it is separated from, that is, it is not in contact with the connector contact J9. When such a state is formed, the substrate J6 is electrically separated from the connector contact J9. Hence, the signal of a sensed pressure value cannot be taken out to the outside.
Moreover, when the compression spring J8 resonates, in some cases, the compression spring J8 in contact with the connector contact J9 vibrates in such a way as to rub the connector contact J9. In this manner, when the other end of the compression spring J8 vibrates, the compression spring J8 and the connector contact J9 are worn. This causes malfunctions that the output from the substrate J6 becomes unstable and that a signal showing a pressure value includes noises.
The above problems easily occur, in particular, when the pressure sensor is mounted in a place where the pressure sensor is susceptible to vibrations (for example, in the engine room of a vehicle).